The present invention relates to a process for depositing salts from supersaturated aqueous solutions of salts or supercooled molten liquids of salts.
A technique of depositing salts as crystals from aqueous solutions or molten liquids thereof has been utilized in various fields.
In general, the solubility of salts in water depends on the kind of the salts and temperature, and the solubility of many salts increases with temperature. When the saturated solution of the salts is cooled, the excess amounts of salts deposit. This phenomenon is frequently utilized as recrystallization to obtain pure salts from aqueous solutions of salts.
When some salts are heated, they melt at a defined temperature to become molten liquids. To the contrary, when molten liquids of the salts are cooled, they solidify at a defined temperature and often release a latent heat. As an application of this phenomenon, there is known a method in which a salt is melted by solar heat or waste heat from factories, and latent heat released at solidification of the salt is utilized with a hot-water supply, preheating or air-conditioning system.
However, the deposition or solidification of salts does not always proceed readily. That is to say, in the former case, a salt often dissolves in amounts more than its solubility at that temperature. Namely, a supersaturated solution is formed and therefor, the deposition does not effectively proceed. In the latter case, the phase transition of a salt from the molten state to the solid state does not occur, even below the transition temperature on cooling. Thus, the salt forms supercooled molten liquid. The supersaturated solution requires a long time and an extra cooling to deposit a salt. The supercooled state makes the supersaturated solution is unusable in an air-conditioning system because latent heat is not released. Agitation of a system or addition of seed crystals to a system have been adopted to prevent the system from supercooling or supersaturation, but their effect is not always sufficient.
It is an object of the present invention to provide a novel process for depositing a salt in a good efficiency from an aqueous solution or molten liquid of the salt.
A further object of the invention is to provide a process for depositing a salt in a simple manner from an aqueous solution or molten liquid of the salt.
Another object of the invention is to provide a process for the prevention of the supersaturation of an aqueous solution of a salt or the supercooling of a molten liquid of a salt.
These and other objects of the present invention will become apparent from the description hereinafter.